The present invention relates to a method of and a device for cooling by means of one or more cooling fluids such as gas, vapor or liquid, a hot product gas exiting from a gasification reactor.
In reactions between the fuel such as for example finely divided coal or other carbonous substances and the means of gasification such as oxygen and possibly steam, there result gasification temperatures between about 1,200.degree. to 1,700.degree. C. Due to the fusion or softening of fuel ashes at high temperatures it is necessary to cool down in a suitable manner the hot product or crude gas exiting from the gasification reactor below the fusion or softening point of ash particles entrained in the crude gas stream in order to prevent the caking and deposition of the ashes in subsequent processing tracks.
The cooling of the hot crude gas also called quenching, can be made by the admixture of cool recycled product gas or of another suitable gas or steam or if need be also of water. The cooling pursues the following two objectives: on the one hand, the inner walls of crude gas channel or duct at the outlet of the gasification reactor should be protected against the hot gas and the bakable ash or cinder particles entrained therein and, on the other hand, the stream of hot gas up to its entry into armored heat exchanger or to a deviation duct should be mixed with the introduced cooling fluid to such an extent that in the entire stream cross-section the temperature is sufficiently low as to preclude the formation of bakable ash or cinder particles. While the attainment of the former objective requires the provision of a streamlined inlet for the cooling medium into the crude gas duct to allow the streaming of the introduced cooling medium as a cool veil spread along the inner wall of the crude gas channel, the fulfillment of the second objective requires the formation of a strong penetration and hence an intensive mixing of both gas streams and/or a relatively long mixing path.
It has been known to introduce the cooling fluid radially inwardly into the crude gas duct. In doing so, the first mentioned objective, namely the protection of the inner walls of the crude gas duct can be achieved through an optimization of the feeding conditions of the cooling fluid. However, to achieve the second objective, namely the homogeneous mixing of the crude gas with the cooling fluids, it is necessary with this kind of mixing to provide a correspondingly long mixing track and hence a correspondingly long crude gas duct.